<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>三种使用 CSS 的方法</title>
    <!--外部CSS-->
    <link rel="stylesheet" href="/基础教程/CSS/mystyle.css">
</head>
<body>
<h1>This is a heading</h1>
<p>This is a paragraph.</p>
</body>
</html>